The Citabria (airbatic spelled backwards) and the Decathalon are two different airplanes, but very similar in flight characteristics. You do not want to try either as a second plane. Both are very aerobatic, but will not be likely to help you with learning aerobatics. Neither would make a good first tail dragger either.

Try the Sig 4 Star or a Great Planes Super Sportster, or do a search for "second plane". You should find at least six or eight good choices.
Dennis-